Currently when there are multiple data sources from Google (bigquery or google sheets) and you want to edit a connection, refresh an extract or simply open a previously created workbook, you must authenticate with Google for each and every data source connected. If you have more than 3 or 4 data sources then this can cause delays and frustration that each time the workbook is opened you have to authenticate 3 or 4 times.
Using other data sources (Amazon Redshift) you could have multiple data sources but if you authenticate for one, it would recognise that the other data sources had the same connection and apply the credentials used. This was so much quicker and easier. Once published on server the credentials could also be edited on server, this could be changing the user's credentials to a service account. Google data sources are not able to do this.